Ignition system for internal combustion engines

ABSTRACT

The ignition coil of an ignition system for internal combustion engines is provided with means for determining precisely the point of time of initiation of coil energization and with means for determining precisely the point of time of energy release, or coil de-energization. This is achieved by a disk rotating in synchronism with the internal combustion engine, markings on said disk and fixed sensor means for reading said markings as they are moved past said sensor means, and discriminator means having a predetermined threshold receiving the output of said sensor means and emitting signals whose timing is a function of the rpm at which said disk rotates past said sensor means.

United States Patent Brungsberg 1 Oct. 28, 1975 IGNITION SYSTEM FORINTERNAL 3,738,339 6/1973 Huntzinger et al. 123/117 R COMBUSTION ENGINES3,756,212 9/1973 Schirmer et a1 123/148 E 3,799,136 3/1974 Korteling123/148 E [75] Inventor: Heinrich-Josef Brungsberg,

Ludenscheid, Germany [73] Assignee: Brown, Boveri & Cie. A. G.,

Mannheim, Germany 9 [22] Filed: Oct. 31, 1973 [21] Appl. No.: 411,522

[30] Foreign Application Priority Data Nov. 10, 1972 Germany 2255044[52] US. Cl. 123/117 R; 123/148 E [51] Int. C1. F02P 5/04 [58] Field ofSearch..... 123/117 R, 146.5 A, 148 E, 123/149 C [56] References CitedUNITED STATES PATENTS 2,852,590 9/1958 Fremon 1. 123/148 E 3,592,1787/1971 Schiff 123/117 R 3,705,573 12/1972 Palazzetti et a1... 123/146.5A 3,719,177 3/1973 Oishi et al 1231/1465 A Primary ExaminerCharles J.Myhre Assistant Examiner-Paul Devinsky Attorney, Agent, or Firm-ErwinSalzer [57] ABSTRACT The ignition coil of an ignition system forinternal combustion enginesis provided with means for determiningprecisely t'he point of time of initiation of coil energization and withmeans for determining precisely the point of time of energy release, orcoil deenergization. This is achieved. by a disk rotating in synchronismwith the internal combustion engine, markings on said disk and fixedsensor means for reading said markings as they are moved past saidsensor means, and discriminator means having a predetermined thresholdreceiving the output of said sensor means and emitting signals whosetiming is a function of the rpm at which said disk rotates past saidsensor means.

5 Claims, 5 Drawing Figures US. Patent Oct.28, 1975 Sheet10f5 3,915,131

1L. P818111 1 0a. 28, 1975 Sheet2 0f5 3,915,131

n (I/min) )joz()in 2ms 1 B()inO,22rns n NUMBER OF REVOLUTIONS PERMINUTE.

q: 0! =ANGLES ENCLOSED BETWEEN REFERENCE POINTS 1 AND 2 AND THE MARKINGSON SIGNALLING DISK LILDIJY.

B =ANGLES ENCLOSED BETWEEN CONTIGUOUS MARKINGS ON SIGNALLING DISK LEDIEUS. Pateht Oct. 28, 1975 Sheet4 of5 3,915,131

FIG,4

magnet-segment 0m. 28, 1975 Sheet 5 of5 3,915,131

U.S., Pam

train of waves train of waves pickup coil band pass filter IGNITIONSYSTEM FOR INTERNAL COMBUSTION ENGINES BACKGROUND OF THE INVENTION Thisinvention relates to ignition systems for internal combustion engines,and more particularly to means for determining the point of time atwhich storage of the energy required for ignition is to begin, and fordetermining the point of time at which the stored energy is to bereleased.

There are many different prior art ignition systems for internalcombustion engines of which all are subject to serious drawbacks andlimitations. Considering igni tion systems involving ignition coilswhose current is interrupted periodically by separating interruptercontacts, since in such systems the aforementioned contacts must carryand must interrupt the entire current flowing through the ignition coil,this results in rapid and serious contact erosion. Such ignition systemsare further subject to the drawback that their ignition coil must carrymuch larger currents when the number of revolutions of the internalcombustion engine is small than required by the quantum of ignitionenergy to be released. When the number of revolutions of the internalcombustion engine is relatively large, the amount of time available isnot sufficient to store inductively the entire quantum of ignitionenergy required, so that the available ignition energy may beinsufficient at relatively high numbers of revolution.

In order to reduce the current-carrying and currentinterrupting duty ofthe contacts of the interrupter, the current of the ignition coil may becontrolled by semiconductor switching devices, so that the contacts ofthe interrupter have to carry and interrupt but the relatively smallcontrol current required by such switching devices. However, the otherdrawbacks of conventional ignition systems referred-to above are noteliminated by the use of semiconductor switching devices for controllingthe current which flows through the ignition coil.

In capacitor ignition systems the energy required for ignition isinitially stored inductively in an intermediate storage means, andtransferred immediately thereafter to an ignition capacitor. There theenergy required for ignition is stored virtually without any loss, untilneeded and released. One particularly desirable feature of such ignitionsystems resides in the fact that the current supplied to the inductiveintermediate storage means may be limited to the extent dictated byignition energy requirements. In other words, since inductiveintermediate storage means do not require a holding current asconventional ignition coils do, and since at small numbers of revolutionthat current is a significant portion of the total current carried byconventional ignition coils, capacitor ignition systems are aconsiderable improvement over conventional ignition coil ignitionsystems. Capacitor ignition systems are, however, subject to a seriousdrawback consisting in that the du ration of the igniting sparks thereofis very short, and in some instances too short to effect ignition of thecombustible air and gas mixture.

It has not been possible, heretofore, to provide eco nomically feasibleignition systems combining the desirable feature of capacitor ignitionsystems, i.e. low energy consumption, and the desirable feature ofconventional ignition coil systems, i.e. sufficient duration of thespark discharge. It is, therefore, the primary object of the presentinvention to provide ignition systems for internal combustion engineswhich combine the desirable features of the two above referred-to priorart ignition systems. Other objects of this invention will becomeapparent as this specification progresses.

If onewishes to store in an ignition coil a predetermined quantum ofignition energy, this calls for a predetermined period of time followingclosing of circuit of the coil. The aforementioned predetermined periodof time depends upon the inductance of the coil. If the required quantumof energy is stored, but not yet needed at the pointof time storage iscompleted, the flow of current must continue. This continued flow ofcurrent is referred-to as holding current. The holding current iseliminated if the circuit of the ignition coil is closed at preciselysuch a point of time that the storage of the required quantum ofignition energy will be completed at the very instant when the ignitionenergy is needed. Hence it is desirable to close the circuit for theignition coil at a preceisely predetermined time prior to the point oftime of ignition or firing of the spark plugs. It is common practice todetermine the point of time of ignition in terms of the angular positionof the crankshaft. This means that the ignition circuit must be closedat a leading angle, which angle increases as the number of revolutionofthe internal combustion engine increases.

SUMMARY OF THE INVENTION A system embodying this invention fordetermining the time of initiation of inductive energy storage in theignition coil of an ignition system for internal combustion enginesincludes a rotatable disk driven to rotate in synchronism with aninternal combustion engine, markings on said disk and fixed sensor meansfor reading said markings when said markings are moved past said sensormeans, and discriminator means having-a predetermined thresholdreceiving the output of said sensor means and emitting signals whosetiming is a function of the number of rpm at which said disk rotatespast said sensor means. The markings on said disk are formed by linesarranged adjacent the periphery thereof and having a progressivelyincreasing angular pitch in the direction of rotation of said disk, andthe discriminator means are formed by coincidence means having twovariable inputs derived from said sensor means and yielding an output incase of coincidence of said two variable inputs.

BRIEF DESCRIPTION OF THE DRAWINGS FIG. 1 is a diagrammaticrepresentation of a first embodiment of the present invention;

FIG. 2 is a table of data relevant to the present inven tion;

FIG. 3, 4 and 5 are diagrammatic representations of other embodiments ofthe present invention.

DESCRIPTION OF PREFERRED EMBODIMENTS FIG. 1 shows a rotatable diskincluding four quadrants I,II;,III,IV. The aforementioned disk is drivenin The signal emitting disk of FIG. 1 is intended to be operativelyrelated to a four cylinder internal combustion engine. Therefore twoignition sparks must be supplied to the internal combustion engine perrevolution thereof. In order to determine the points of time at whichenergy storage must begin, the aforementioned quadrants [and II areprovided with marks a and h which may be formed by short radiallyextending lines arranged close to the periphery of quadrants l and III.Reference numerals l and 2 have been applied to indicate two fixedreference points on signalling disk I,II,III,IV. The spacing betweencontiguous reference marks or reference lines a,b increasesprogressively for leading angles, or in counter-clockwise direction. Thetwo reference points 1,2 correspond to ignition angles of and 180 forthe two cylinders which must be supplied with ignition sparks at eachrevolution of the crankshaft.

As shown in FIG. 1 the signalling disk 1,II,III,IV has just reached sucha position that its reference point 1 between its quandrants II and IIIis juxtaposed to a sensor 3. The output signal of sensor 3 is suppliedby two parallel lines to the input terminals of an AND-gate 4. One ofthese two lines interconnects sensor 3 directly with one of the twoinputs of gate 4. The other of these two lines interconnects sensor 3 bythe intermediary of delay line with the other of the two inputs of gate4. The output of gate 4 is a signal initiating the storage of energy.

Supposing it is intended to use an ignition coil requiring 2 msec forstoring the required quantum of ignition energy; then storage of thatenergy must begin at a point of time 2 msec before the crankshaftreaches a reference point, which point of time, in turn, depends uponthe number of revolution of the internal combustion engine. It may beassumed that delays in the circuits are in the order of and in viewthereof delay line 5 may have a delay time of 0.22 msec. The table ofFIG. 2 has been calculated on the basis of the above assumptions. Column1 of the table indicates number of revolutions per minute from 6000 downto 591. Column 2 of the table indicates for given numbers of rpm theangles a which are the angles enclosed between the reference points 1and 2 and the various markings on signalling disk I,II,III,IV. Column 3indicates for given numbers of rpm the angles B which are the anglesenclosed between contiguous markings on signalling disk I,II,III,IV. Theangles a and ,8 have also been indicated in FIG. 1. The angles a statedin column 2 are the travel of disk I,II,III,IV at the number of rpmindicated in column 1 during a time interval of 2 msec. The same appliesin regard to the angles [3 indicated in column 3 in regard to timeintervals of 0.22 msec.

Assuming the crankshaft of the internal combustion engine rotates at6000 rpm, and that the first of the marks a just passes by sensor 3. Asa result, sensor 3 supplies a pair of signals to AND-gate 4, onedirectly,

and the other by the intermediary of delay line 5 having 7 a time delayof 0.22 msec. Since this pair of signals does not reach AND-gate 4simultaneously, the latter has no output at this point of time.Thereafter, the next following mark a passes sensor 3, as a result ofwhich sensor 3 supplies gate 4 with another pair of signals. Now one ofthe input terminals of gate 4 receives a delayed input signal resultingfrom the first mark on disk I,II,III,IV, and the other of the inputterminals of gate 4 receives a non-delayed input signal resulting fromthe second mark on disk I,II,III,IV. Hence there is a coincidence ofinput signals at AND-gate 4, and the latter emits an output signalinitiating the process of storing energy in the ignition coil of thesystem. All subsequent output signals of sensor 3 which follow oneanother at progres' sively decreasing intervals may establish conditionsinput coincidence at AND-gate 4, and thus cause the latter to emitoutput signals. This is of no consequence since it is the first outputsignal of AND-gate 4 which initiates the energy storage process in theignition coil, and since the subsequent output signals of AND-gate 4have not effect on that process, i.e. do not interrupt or disturb thesame.

When the number of revolutions per min. is less than 6000, the timeinterval between the signals of the sensor 3 resulting from the firstmark a and the second mark a is so long that the delayed signalresulting from the first mark a has disappeared at one of the inputs ofgate 4 at the time when the non-delayed signal resulting from the secondmark a arrives at the other of the inputs of gate 4. Then no outputsignal is emitted from gate 4. Under such circumstances a coincidence ofa delayed signal resulting from one mark a with a nondelayed signalresulting from a subsequent mark a will occur only at smaller leadingangles of disk I,II,III,IV and its driving crankshaft, respectively.

Upon termination of the energy storage or loading period reference mark1 and sensor 6 cooperate to produce an ignition or firing signal.

The next energy storage or loading period is determined by the passageof marks b near sensor 1 in substantially the same fashion as the firstenergy storage or loading period has been determined.

In instances where the ignition coil forms part of a blocking oscillatorthe output of AND-gate 4 is used as a trigger signal for the blockingoscillator which generates the ignition spark following a period of timedetermined by the time constant thereof.

There are instances where it is desirable to actively control therelease of ignition energy from the ignition coil and it may beacceptable to allow the flow of a holding current of limited magnitudeand to interrupt the flow of that current at the point of time ofignition. In such instances marks of reference points 1 and 2 maygenerate signals in sensor 6 which, in turn, cause interruption of theholding current or triggering of a thyristor.

It is apparent from the above that in the embodiment of the inventionshown in FIG. I intended for a four cylinder internal combustion enginemarks a and b are arranged in the first quadrant I and in the thirdquadrant III of disk I,II,III,lV at and 0, respectively, which marksdetermine jointly with sensors 3 and 6 the beginning of the energystorage time and the ignition time. The delay line 5 causes a delayedcoincidence between two signals resulting from two consecutive marks.The same principle, namely the determination of delayed coincidence oftwo signals to determine the point of time of initiation of energystorage, or ignition coil loading, may be embodied by other means thanthose shown in FIG. 1, e.g. by the means shown in FIG. 3.

Referring now to FIG. 3, the same reference characters have been appliedin that figure as in FIG. 1 to indicate like parts. Hence the system ofFIG. 3 calls for description only of such elements thereof which differfrom those of the system shown in FIG. I. The principaldifference'betweenthe system of FIG. I and that of FIG. 3 residesin'the" fact that'inthesystem of FIG. 3 the individual marks a and bwhichcorrespond to each other: are not angularly displaced exactly180%The 24 marks b of FlGJ-3 encompass an angular, range whichcorresponds to'that of 23 marks in the system of FIG. .1. Furthermore asensor has been added towhich reference character 10 has been applied.Sensor 10 isarranged at the 270 position of four quadrant diskI,II,III,IV. In the system of FIG. 3 th e'delay line 5 and the AND gate4 of FIG. 1 have been dispensedwith, or eliminated. The outputs ofsensors 3 and 6 form the inputs of a coincidence module 11. Referring toFIG. 3 and comparing the same with FIG. 1, in the former the referencemarks 1 and 2 have been angularly displaced 90 relative to the markingsa and b, respectively.

As mentioned above, markings a,b are not angularly displaced 180 buthave a smaller angular displacement comparable to the marks of avernier. Hence sensors 3 and 6 emit signals which are delayed onerelative to the other. The delay times of these signals is a function ofthe number of rpm of disk I,II,III,IV. If two such signals coincide intime, module 11 emits a signal which initiates the storage of magneticenergy in the ignition coil. When reference marks 1 and 2 sweep passedsensor 10 an ignition or firing signal is emitted by the latter.

The circuitry of FIG. 3 is even more desirable than that of FIG. 1,primarily because it does not require delay means and hence possiblevariations in regard to delay times. In addition thereto the structureand circuitry of FIG. 3 makes it possible to determine in a simple waywith a high degree of precision the point of time at which theenergization of the ignition coil should be initiated because in theembodiment of FIG. 3 the number of marks on disk I,II,III,IV may beincreased, and the coincidence times of module 11 shortened.

The embodiment of the invention shown in FIG. 3 is particularly suitableto be used in conjunction with ignition coils forming part of a blockingoscillator to adjust the angles of ignition as a function of the numberof revolutions per minute of the internal combustion engine. The desiredadjustment of the firing angle may be achieved merely by positioning themarks on disk I,II,III,IV. On the other hand, the resolution ofcoincidence module 11 may be varied as, for instance, by means of adiscriminator, the exact firing time depending upon the resolution ofmodule 11.

In the embodiments of the invention which have been described above themeasured quantity was the time relation between two marks. In oneembodiment of the invention the time relation was ascertained bycoincidence of a signal resulting from one mark and of a delayed signalresulting from a previous mark. In another embodiment of the inventionthe time relation was ascertained by means of two signals which weregenerated by two marks each pertaining to one group of marks. Thediscriminator required in such an instance is a time discriminator andthe threshold value to be adjusted by it is the resolution ofcoincidence module 11.

There are, however, still other ways to achieve the desired end. It iswell known that the voltage which is induced in a winding or coil isproportional to the rate of change of a magnetic flux. If marks on arotating disk are formed by magnetic teeth or the like, the voltagepulses induced in a magnetic sensor cooperating with the disk areproportional to the number of rpm at which the disk is rotated past: thesensor. The spacing between magnetic teeth of a disk and anelectromagnetic sensor may vary, e.g. the length or height of such teethmay decrease the larger the leading angle thereof.

' It is possible to generate by means of such an arrangement signalswhich depend upon the respective number of rpm of the disk and may beused for controlling the point of time of initiation of energization ofan ignition coil. Considering a disk whose leading magnetic teeth have arelatively small height, resulting in a relatively large spacing from acooperating electromagnetic sensor, and whose trailing magnetic teethhave a relatively small height, resulting in a relatively small spacingfrom a cooperating electromagnetic sensor. In such an arrangement aleading magnetic tooth of relatively small height rotating past anelectromagnetic sensor at a relatively large distance may be capable ofgenerating in the latter a sufficiently high voltage pulse to causeinitiation of energization of an ignition coil.

Another possibility consists in providing the rotatable disk with marksin the shape of a train of waves having a wave length that increasesprogressively as the leading angle from a fixed reference pointincreases. As the disk rotates the train of wave marks is sensed by afixed sensor and converted into a corresponding electric signal. Thelatter is supplied to a narrow band-pass filter which passes a signalif, and only if, the product of angular velocity of the disk and thewave length of its marks lies within the band of frequencies passed bythe filter.

The means by which the marks on the rotating disk are sensed by thesensors has no immediate bearing on the present invention. The marks onthe disk may be scanned either electro-optically, or inductively. Theoutput signals of the sensors may be processed either by analog means orby digital means. The threshold discriminators applied in embodying thepresent invention may be time discriminators, voltage discriminators, orcurrent discriminators, the particular kind of discriminators used beingdependent upon the particular circumstances under consideration.

I claim as my invention:

1. In an ignition system for internal combustion engines including meansfor inductively storing and for controlling the point of time ofinitiation of energy storage including in combination a. a rotatabledisk driven to rotate in synchronism with an internal combustion engine;

b. markings on said disk and fixed sensor means for reading saidmarkings when said markings are moved past said sensor means;

0. discriminator means receiving the output of said sensor means andemitting signals whose timing is a function of the rpm at which saiddisk rotates past said sensor means;

2. An ignition system as specified in claim 1 wherein markings on saiddisk cooperate with additional fixed sensor means emitting timingsignals for energy release from the inductive storage thereof.

3. An ignition system as specified in claim 1 wherein said coincidencemeans are formed by an AND-gate having two inputs of which one input issupplied directly from a marking sensor and the other input is suppliedfrom said marking sensor by the intermediary of a delay line.

4. In an ignition system for internal combustion engines including meansfor conductively storing ignition energy and for controlling the pointof time of initiation of energy storage the combination of a. a rotabledisk driven to rotate in synchronism with an internal combustion engine;

b. markings on said disk and fixed sensor means for reading saidmarkings when said markings are moved past said sensor means, saidmarkings being formed by lines arranged immediately adjacent to theperiphery of said disk and having a progressively increasing angularpitch in the direction of rotation of said disk; and

c. discriminator means receiving the output of said sensor means andemitting signals whose timing is a function of the number of rpm atwhich said disk of said pair of sensors.

1. In an ignition system for internal combustion engines including meansfor inductively storing and for controlling the point of time ofinitiation of energy storage including in combination a. a rotatabledisk driven to rotate in synchronism with an internal combustion engine;b. markings on said disk and fixed sensor means for reading saidmarkings when said markings are moved past said sensor means; c.discriminator means receiving the output of said sensor means andemitting signals whose timing is a function of the rpm at which saiddisk rotates past said sensor means; d. said markings on said disk beingformed by lines arranged adjacent to the periphery of said disk andhaving a progressively increasing angular pitch in the direction ofrotation of said disk; and e. said discriminator means being formed bycoincidence means having two variable inputs derived from said sensormeans and yielding an output in case of coincidence of said two variableinputs.
 2. An ignition system as specified in claim 1 wherein markingson said disk cooperate with additional fixed sensor means emittingtiming signals for energy release from the inductive storage thereof. 3.An ignition system as specified in claim 1 wherein said coincidencemeans are formed by an AND-gate having two inputs of which one input issupplied directly from a marking sensor and the other input is suppliedfrom said marking sensor by the intermediary of a delay line.
 4. In anignition system for internal combustion engines including means forconductively storing ignition energy and for controlling the point oftime of initiation of energy storage the combination of a. a rotabledisk driven to rotate in synchronism with an internal combustion engine;b. markings on said disk and fixed sensor means for reading saidmarkings when said markings are moved past said sensor means, saidmarkings being formed by lines arranged immediately adjacent to theperiphery of said disk and having a progressively increasing angularpitch in the direction of rotation of said disk; and c. discriminatormeans receiving the output of said sensor means and emitting signalswhose timing is a function of the number of rpm at which said diskrotates past said sensor means, said discriminator means being formed bya coincidence gate having two inputs, one of said two inputs beingdirectly supplied by the output of said fixed sensor means and the otherof said inputs being supplied by said fixed sensor means by theintermediary of a timedelay line.
 5. An ignition system as specified inclaim 1 including a pair of angularly displaced sensors, a coincidencemodule supplied with the outputs of said pair of sensors and twoangularly displaced groups of markings on said disk, each arranged to beread simultaneously by one of said pair of sensors.